An apparatus comprising all the above features is described in U.S. Pat. No. US-A-3905116 to Roberts. In particular, said patent relates to a crankshaft measuring apparatus including a main frame which carries two preliminary alignment V blocks, a headstock with a spindle nose and a tailstock with a dead centre, for supporting the crankshaft to be checked, and a carriage. The carriage comprises a part supporting a probe, said part being pivotable about an axis parallel to the axis defined by nose and dead centre.
In this known apparatus the axis of rotation of the structure carrying the sensing means, that is the probe, is arranged substantially beside and behind with respect to the position of the workpiece geometrical axis defined by the rest devices - that consist in the spindle nose and the dead centre -, by considering as front and rear parts of the apparatus those located at the operator's side and the opposite side, respectively. Consequently, the accessibility of the apparatus during the workpiece loading and unloading phases is not satisfactory, the overall dimensions in a transversal and/or vertical direction are considerable and there are also considerable risks of the workpiece possibly colliding against and damaging the sensing means.